Peripheral fatigue
Also known as: Local fatigue
Peripheral fatigue is an exercise-induced reduction in a muscle's capacity to produce force because of processes at or beyond the neuromuscular junction. It occurs within the muscle membrane, excitation–contraction processes, or contractile machinery rather than through a reduction in voluntary drive from the brain or spinal cord.
During repeated contractions, several factors can alter how effectively an electrical signal produces force. Their contribution depends on the task, load, contraction duration, muscle, training status, and time since exercise. Central fatigue can occur at the same time, so a decline in repetitions or bar speed does not identify a purely peripheral cause. Laboratory studies often compare voluntary performance with the force evoked by nerve stimulation, a method that is not available from an ordinary workout log. A review of fatigue and performance cautions against assuming that a descriptive label precisely locates the limiting mechanism.
"Local fatigue" is the practical coaching description: the trained muscle becomes less able to sustain the intended output during or after a set. It may contribute to reaching muscle failure and to lower performance in later sets that use the same muscles. Changing the exercise, lengthening the rest interval, stopping farther from failure, or reducing set volume may reduce the immediate local demand, but the appropriate choice depends on the session's purpose.
Peripheral fatigue is not synonymous with a burning sensation, lactate accumulation, a pump, muscle damage, or delayed-onset muscle soreness. These experiences can overlap without being interchangeable, and soreness is not required for peripheral fatigue. Recovery also occurs at different rates for different processes. Performance in the relevant movement, assessed under comparable conditions, is therefore more informative than relying on one sensation or a fixed recovery clock.